Process for production of oxidized polyisobutenes, their use in the production of additives and use of the additives

ABSTRACT

Oxidised polyisobutenes, that is polyisobutenes containing ketonic and carboxylic acid carbonyl groups, are produced by passing through a column of the polyisobutene maintained at a temperature in the range from 140° to 200° C. and at atmospheric or elevated total pressure a molecular oxygen-containing gaseous oxidant at a gas flow rate greater than 10 liters cm -2  h -1  measured at the operating pressure. The oxidized polysisobutenes can be reacted for example with an aliphatic polyamine to produce a lubricating oil additive or with an aliphatic polyamine and formaldehyde to product a fuels additive.

This is a division of application Ser. No. 07/216,634, filed June 24,1988, now U.S. Pat. No. 5,028,666.

The present invention relates to an improved process for the productionof oxidized polyisobutenes, to the production of lubricating oil andfuel additives therefrom and to the uses thereof.

Oxidized polyisobutenes, that is polyisobutenes having oxygen chemicallybound thereto principally in the form of keto-carbonyl groups, arepotentially valuable industrial products because they are readilyconvertible by reaction with amines into materials useful as lubricatingoil additives, for example as dispersants and detergents.

The oxidation and subsequent ammination of polyisobutylenes has beendescribed in the patent literature in, for example, U.S. Pat. No.4,931,024.

U.S. Pat. No. 3,931,024 discloses that a highly effective dispersant fora lubricating oil or a fuel can be prepared by the noncatalyzedair-oxidation of a polyolefin or of a halogenated polyolefin to form anoxygen-containing material. This material is then reacted with analiphatic polyamine under conditions that cause the formation of anaddition product which differs chemically from the Schiff bases of theprior art. The oxidation of the polymer is conducted by contacting thepolymer with air at a temperature in the range of from about 120° toabout 250° C., more usually at a temperature in the range from about150° C. to about 220° C. The lower temperatures tend to favor moreunsaturation in the product. Excessively high temperatures are generallyto be avoided so as to minimize degradation. Atmospheric pressure orsomewhat elevated pressures can be used, the latter favoring the masstransfer rate. Efficient agitation is also helpful in increasing therate. In Example 1 of U.S. Pat. No. 3,931,024 a quantity ofpolyisobutene of about 980 average molecular weight was oxidized byblowing air through the polymer at 170° C. for 25 hours, no catalystbeing used. More specifically, 1640 g of the polymer was thus oxidizedusing a stream of air at the rate of 1 liter of air per minute measuredat standard conditions. The oxidized polymer was found to contain 4.3weight percent of oxygen. No further details of the oxidation processare given.

In our experience, it is possible to successfully produce oxidizedpolyisobutenes in stirred pots on a laboratory scale, but scale-up hasproved impossible. This failure to scale-up we now believe is due to thedifficulty involved in developing sufficient shear in a large stirredpot reactor. For example it has been calculated from our results that an80 cm diameter reactor with an 80 cm fill height and a 6 blade flatagitator would require a minimum of a 60 kilowatt stirrer.

In GB-A-959362 there is described the oxidation of polyethylene waxes invessels of 10 liters and 100 liters capacity. In order to achieve anacceptable shear rate a very high agitator power input is employed.

It is clear from the forgoing that for commercial scale operation adifferent approach is required. We have now found that polyisobutenescan be successfully oxidized in a manner capable of use on a commercialscale by passing through a column of polyisobutene a molecularoxygen-containing gaseous oxidant at high gas flow rates per unitcross-sectional area. In this manner high shear of the polyisobutene canbe achieved.

Accordingly, the present invention provides a process for the productionof an oxidized polyisobutene which process comprises passing through acolumn of the polyisobutene maintained at a temperature in the rangefrom 140° to 200° C. and at atmospheric or elevated total pressure amolecular oxygen-containing gaseous oxidant at a gas flow rate greaterthan 10 liters cm⁻² h⁻¹ measured at the operating pressure.

As the molecular weight of polyisobutenes increases, their physical formchanges from mobile liquids, through viscous liquids to rubbery solids.Suitably the polyisobutenes may be one having a number average molecularweight in the range from about 900 to about 10,000, though highermolecular weight polyisobutenes may be used if desired. Low molecularweight polyisobutenes are mobile liquids and may therefore be used inthe absence of a solvent. However, it may nevertheless be desirable touse a low molecular weight polyisobutene dissolved in a suitable solventand for higher molecular weight polybutenes the use of a solution in asuitable solvent is essential. Suitable solvents are those whichdissolve the polybutene and are not detrimentally oxidized or otherwisechemically attacked under the process conditions. Suitable solventsinclude hydrocarbon liquids which may be aliphatic or aromatic, forexample a base oil, typically a solvent neutral oil, a low molecularweight polyisobutene, liquid paraffins, benzene, a chlorinated benzene,and the like.

The column of polyisobutene may suitably be contained within a tubularreactor. A preferred form of tubular reactor is a draft tube reactor,i.e. a reactor which comprises a closed vessel having at least one inletand at least one outlet, a partition dividing the vessel into two zoneswhich intercommunicate above and below the partition and means foradmitting gas in a finely divided state into the lower part of one ofthe zones. The use of a draft tube reactor facilitates good mixing, afeature identified as being desirable on scale-up, by returning materialfrom the top of the reactor to the base. Another feature, identified asbeing relevant to the achievement of optimum results, is the height ofthe liquid column. Desirably, the static height of the liquid column,that is the height of the liquid column in the non-operative mode,should be greater than 30 cm, irrespective of the cross-sectional areaof the column.

An important parameter is the temperature of the polyisobutene.Oxidation does not occur at an appreciable rate at temperatures muchbelow 140° C. and at temperatures above 200° C. the polyisobutene tendsto `crack` to lower molecular weight hydrocarbons at an appreciablerate. The polyisobutene is preferably maintained at a temperature in therange from 150° to 190° C., even more preferably at about 180° C.

The molecular oxygen-containing gaseous oxidant should be of acomposition such as to remain outside the explosive limits of any lighthydrocarbons formed during the oxidation. A suitable gaseous oxidant forthis purpose is oxygen diluted with inert gas, for example nitrogen.Preferably in such a mixture the oxygen concentration is in the rangefrom 2 to 20% by volume, more preferably about 10% by volume. Air orother molecular oxygen-containing gases may also be used, subject to theaforementioned proviso. It is preferred to recycle the gaseous oxidantafter passage through the polyisobutene since only a small proportion ofthe available oxygen is absorbed per pass through the column ofreactant.

The molecular oxygen-containing gas is preferably passed through thecolumn of polyisobutene at a gas flow rate greater than 20, morepreferably greater than 40 liters cm⁻² h⁻¹.

Although the process may be operated at atmospheric pressure it ispreferred to operate at elevated gaseous total pressures in order tocompensate for low molecular oxygen concentrations. Suitably oxygenpartial pressure up to 1.5 bar at total pressures up to 15 bar may beemployed, though higher pressures may be used.

The process may be operated batchwise or continuously, preferablycontinuously.

The product of oxidizing a polyisobutene by the aforedescribed processis a polyisobutene with a suitable chemically bound oxygen content, theoxygen being incorporated principally in the form of keto carbonyl orcarboxylic acid groups.

The oxidized product is a useful chemical intermediate which may befurther reacted to produce materials useful as lubricating oil and fueladditives, as well as adhesives and fillers.

In a further embodiment therefore the present invention provides aprocess for the production of a product suitable for use as alubricating oil additive which process comprises reacting an oxidizedpolyisobutene produced by the process as hereinbefore described with analiphatic polyamine employing a mole ratio of polyamine to oxidizedpolyisobutene of from about 0.2 to about 2.5 moles of polyamine per moleof the oxidized polyisobutene.

Further details of this process may be found in the aforesaid U.S. Pat.No. 3,931,024, the disclosure of which is incorporated herein byreference.

The invention also provides a finished lubricating oil compositioncomprising a major proportion of a lubricating oil and a minorproportion of a lubricating oil additive prepared by the process ashereinbefore described.

The lubricating oil may suitably be any oil of lubricating viscosity andmay be either natural or synthetic.

In a preferred embodiment the invention also provides a process for theproduction of a product suitable for use as a fuel additive for inletmanifold and carburettor detergency which process comprises reacting anoxidized polyisobutene produced by the process as hereinbefore describedwith an aliphatic polyamine, preferably an alkylene polyamine, andformaldehyde or a precursor thereof.

The aliphatic polyamine is preferably an alkylene polyamine having thegeneral formula:

    NH.sub.2 (CH.sub.2).sub.n --[NH(CH.sub.2).sub.n ].sub.m NH.sub.2

wherein n is from 2 to 4 and m is a number from 0 to 10. Specificcompounds falling within the aforesaid formula include ethylene diamine,diethylene triamine, triethylene tetramine, tetraethylene pentamine,propylene diamine, dipropylenediamine, and the like. A preferredalkylene polyamine is diethylene triamine.

With the aliphatic polyamine there can be reacted either formaldehydeitself or a formaldehyde precursor, for example formalin,paraformaldehyde, other linear and cyclic formaldehyde polymers andgaseous formaldehyde.

Conditions under which the reaction may be effected are well known inthe art and require no further elaboration to a person skilled in theart.

In a further embodiment the invention also provides a fuel compositioncomprising a major proportion of a fuel and a minor proportion of thefuel additive prepared by the process as hereinbefore described.

The fuel may suitably be an internal combustion engine fuel. A preferredfuel is one suitable for use in spark ignition engines, for example amotor gasoline. Alternatively, the fuel may be a fuel suitable for usein spark compression engines, for example a diesel fuel.

A preferred embodiment of the invention will now be described withreference to the accompanying FIGURE which takes the form of a flowsheet.

With reference to the FIGURE, 1 is a draft tube reactor having an inlet2 for entry of liquid polyisobutene (PIB) an outlet 3 for discharge ofoxidized PIB, a sparge plate 4, a draft tube 5 and an outlet for gaseousmaterials 6. 7 and 8 are condensers and 9 is a centrifugal blower. 10 to14 are connecting lines.

To the draft tube reactor 1 charged through inlet 2 to about a third itsheight with the polyisobutene to be oxidized and maintained at thedesired temperature (heating means and controls not shown) is fedthrough the sparge plate 4 gaseous oxidant at a gas flow rate greaterthan 10, preferably greater than 20, more preferably greater than 40liters cm⁻² h⁻¹ in the form of fine bubbles. The gaseous oxidant iscomposed of air make up fed through line 10 plus bleed to vent (based onPIB charge) and through line 14 recirculated oxidant controlled at 10%oxygen in nitrogen.

In passing upwards through the column of PIB the gaseous oxidant causesthe PIB level to rise to about two thirds the height of the reactor andproduces a density differential resulting in circulation of the PIBthrough the draft tube, thereby causing mixing.

Through the reactor exit 6 emerges a gaseous mixture comprisingnitrogen, unreacted oxygen and hydrocarbons. This is passed through line11 to the condenser 7 in which condensate comprising light hydrocarbonsand PIB is separated from O₂ and N₂. A part of the O₂ /N₂ mixture isrecirculated through lines 12 and 14 through the centrifugal blower 9.Another part is taken through line 13 by way of a flow regulator and acondenser 8 to vent.

Oxidized PIB is recovered through outlet 3.

EXAMPLE 1

The flow scheme shown in the FIGURE was employed except that items 2, 3,5, 9, 12 and 14 were omitted. The process was operated on a once-throughbasis, i.e. batchwise.

The reactor 1 was charged to a third its height with polyisobutene(Hyvis (RTM) 30, ex BP Chemical Limited, having a number averagemolecular weight of 1350) (approximately 4 liter) and maintained at 180°C. (heating means and controls not shown). Gaseous oxidant consisting of10% oxygen in nitrogen was fed through the sparge plate 4 at a gas flowrate of 45 liters cm⁻² h⁻¹ in the form of fine bubbles. The totalpartial pressure in the reactor was 6.9 barg (100 psig).

A sample of the oxidized polyisobutene was withdrawn from the reactorafter 1 hour through the outlet 3.

The increase in the carbonyl content of the oxidized PIB was observed bymeasurement of the i.r. absorbance at 1720 cm⁻¹, and the total oxygencontent was measured by a microanalytical technique.

The results are given in Table 1.

EXAMPLE 2

The procedure of Example 1 was repeated except that the sample waswithdrawn after 4 hours operation.

The results are given in Table 1.

                  TABLE 1                                                         ______________________________________                                                i.r. Absorbance                                                                             Total O.sub.2                                                                             Mol. Ratio                                  Example (peak height mm)                                                                            Content (%) PIB/O.sub.2                                 ______________________________________                                        Starting                                                                               3            0.04        0.0                                         PIB                                                                           1       15            0.99        0.8                                         2       48            3.52        2.9                                         ______________________________________                                    

EXAMPLE 3

In a small scale glass laboratory reactor the initial oxygen absorptionrate was determined at several different air flowrates per unit crosssectional area (csa) of the reactor for a fixed height of polyisobutenein the reactor.

The results are given in the following Table.

                  TABLE                                                           ______________________________________                                        Initial rate                                                                  (mol O.sub.2 absorbed/mol                                                                     Airflow rate per unit                                         polyisobutene/hour)                                                                           csa (liters cm.sup.-2 h.sup.-1)                               ______________________________________                                        0                0                                                            0.175           20                                                            0.235           34                                                            0.250           45                                                            ______________________________________                                    

EXAMPLE 4 - Oxidized PIB amination

4% w/w diethylene triamine was added to a PIB oxidate and the mixtureheated for 2 hours at 160°-180° C. The mixture was then cooled atapproximately 100° C. To the cooled mixture was added 3% w/w of a 38%solution of formaldehyde in water and the mixture was then heated to180° C. for 1 hour. It was then vacuum stripped at 180° C. to about 10torr, cooled and discharged.

The analytical results are shown in Table 2.

                  TABLE 2                                                         ______________________________________                                                 Basic        Total    Viscosity                                      Oxidate  Nitrogen     Nitrogen at 100° C.                              Sample   (% w/w)      (% w/w)  (cSt)                                          ______________________________________                                        1 hour   NA           0.45     NA                                             oxidate                                                                       4 hour   0.67         0.98     722                                            oxidate                                                                       ______________________________________                                    

The aminated product produced from the 4 hour oxidate 3 was used at atreatment level of 500 ppm in petrol and subjected to a comparative OpelKadett carburettor test. This material compared favorably with acommercial carburettor detergent.

Comparison Test

For the test a 200 liter acid-resistant steel `pot` reactor equippedwith thermostatically controlled electrical heating was used. It wasfitted with a propellor stirrer with provision for introducing gas intothe fluid stream just upstream of the propellor. The air inlet wasfitted with a gas flow meter capable of measuring up to 50 l ofair/minute and a continuous oxygen meter was installed in the exhaustline, which was vented to the outside atmosphere.

The reactor was charged with 100 kg of a polyisobutene of molecularweight 1300 and finely ground potassium carbonate (500 g) as catalyst.Air was then introduced beginning at a very low rate, the intentionbeing to find the maximum permissible air rate when the oxygen contentof the exhaust for safety reasons was not permitted to exceed 5% vol.The rate of air-blowing was increased but never achieved a valueapproaching 10 liters cm⁻² h⁻¹.

After an induction period of a few minutes, the oxidation proceeded veryrapidly. The oxygen content of the exhaust gas never increased above afew percent volume.

After 16 hours reaction time little polyisobutene oxidation hadoccurred, although oxygen consumption was high. This was due to theformation of low boiling (and low flash point) oxygenates.

The oxidation was continued for at least 50 hours and gave a product ofalmost the desired carbonyl content. However, the product was of anundesirable color and, more importantly, gave a lubricating oil andkerosene-insoluble product when reacted with amines.

This is not an example according to the present invention because theair flow rate was less than 10 liters cm⁻² h⁻¹ and is included only forthe purpose of demonstrating that large-scale operation in a stirred potreactor at low oxidant gas flow rates, i.e. less than 10 l cm⁻² h⁻¹,does not produce oxidized polybutenes of a type desirable for furtherprocessing into lubricating oil and fuel additives.

I claim:
 1. A process for the production of a product suitable for useas a lubricating oil additive which process comprises passing through acolumn of polyisobutene maintained at a temperature in the range from140° to 200° C. and at atmospheric or elevated pressure a molecularoxygen-containing gaseous oxidant at a gas flow rate greater than 10liters cm⁻² h⁻¹ measured at the operating pressure to obtain an oxidizedpolyisobutene and then reacting the oxidized polyisobutene with analiphatic polyamine employing a mole ratio of polyamine to oxidizedpolyisobutene of from about 0.2 to about 2.5 moles of polyamine per moleof the oxidized polyisobutylene.
 2. A process for the production of aproduct suitable for use as a fuel additive for inlet manifold andcarburetor detergency which process comprises passing through a columnof polyisobutene maintained at a temperature in the range from 140° to200° C. and at atmospheric or elevated pressure a molecularoxygen-containing gasseous oxidant at a gas flow rate greater than 10liters cm⁻² h⁻¹ measured at the operating pressure to obtain an oxidizedpolyisobutene and then reacting said oxidized polyisobutene with analiphatic polyamine and formaldehyde or a precursor thereof.
 3. Aprocess according to claim 1 or 2 wherein the gas flow rate is greaterthan 20 liters cm⁻² h⁻¹ measured at the operating pressure.
 4. A processaccording to claim 1 or claim 2 wherein the column of polyisobutene iscontained within a tubular reactor.
 5. A process according to claim 4wherein the tubular reactor is a draft tube reactor.
 6. A processaccording to claim 1 or claim 2 wherein the static height of the liquidcolumn is greater than 30 cm, irrespective of the cross-sectional areaof the column.
 7. A process according to claim 1 or claim 2 wherein thepolyisobutene has a number average molecular weight in the range fromabout 900 to about 10,000.
 8. A process according to claim 1 or claim 2wherein a solvent for the polyisobutene is employed.
 9. A processaccording to claim 1 or claim 2 wherein the gaseous oxidant is oxygendiluted with inert gas.
 10. A process according to claim 1 or claim 2wherein the polyisobutene is maintained at a temperature in the rangefrom 150° to 190° C.
 11. A process according to claim 1 or claim 2wherein the oxygen partial pressure is up to 1.5 bar at a total pressureup to 15 bar.
 12. A process according to claim 1 or claim 2 whenoperated continuously.
 13. A process according to claim 2 wherein thealiphatic polyamine is an alkylene polyamine having the general formula:

    NH.sub.2 (CH.sub.2).sub.n --[NH(CH.sub.2).sub.n ].sub.m NH.sub.2

wherein n is from 2 to 4 and m is a number from 0 to
 10. 14. A processaccording to claim 13 wherein the alkylene polyamine is diethylenetriamine.